#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	float sum = 0;
	int flag = 1, i;
	for (i = 1; i <= 100; i++)
	{
		sum += (1.0 / i) * flag;
		flag = -flag;
	}
	printf("%f\n", sum);
	return 0;
}